1. Field of the Invention
The present invention relates to a flexible circuit sheet that will be connected to an electric device. The present invention also relates to a continuous tape having a plurality of flexible circuit sheets thereon. The present invention further relates to an ink jet head that uses the flexible circuit sheet, and a method of producing the same.
2. Description of the Related Art
An ink jet head of an ink jet printer comprises a passage unit and an actuator unit. The passage unit comprises a plurality of pressure chambers, and a plurality of nozzles. Each pressure chamber communicates with one corresponding nozzle. The actuator unit comprises a plurality of actuators. Each actuator is coupled to one corresponding pressure chamber. The actuator unit selects and actuates one or more actuators from amongst the plurality of actuators. When an actuator is actuated, energy is applied to ink that is stored in the pressure chamber corresponding to that actuator, and ink is jetted from the nozzle corresponding to that pressure chamber. An example of an actuator unit is disclosed in Japan Laid-Open Patent Application Publication 2002-36568.
An actuator is an electric device that uses electrical energy to apply pressure to ink. An actuator unit is a device that is an accumulation of electric devices. Electric wirings must be connected to the actuator unit in order to transmit electrical energy to the actuator unit. Because one or more actuators from amongst the plurality of actuators must be selected and actuated independently, electrical wiring must be connected to each actuator. The number of electric wirings connected to the actuator unit must be equal to or larger than the number of actuators.
A flexible circuit sheet is used in order to connect the electric wirings to the actuator unit. The flexible circuit sheet has a flexible base sheet and electric wirings formed on the base sheet.
An electric terminal is formed on each actuator, and a land is formed on each electric wiring, in order to connect the actuators and the electric wirings. Lands, as used in the present specification, are fixed to the electric terminals, and conduct electricity between the electric wirings and the electric terminals. When the arrangement pattern of the lands formed on the flexible circuit sheet matches the arrangement pattern of the electric terminals formed on the actuator unit, each electric wiring is connected to one corresponding electric terminal by fixing the flexible circuit sheet to the actuator unit. A variety of methods are used in order to fix the electric terminals to the lands. Both may be connected together with solder, both may be fixed together with a conductive adhesive, or both may be welded together.
If one actuator is connected to one electric wiring, the actuator to be actuated can be selected by selecting the electric wiring to which electrical energy will be applied. By selecting the actuators to be actuated, the nozzles that will jet ink can be selected. In addition, by controlling the timing at which electrical energy is applied to the electric wirings, the timing at which ink is jetted from the nozzles can be adjusted.
In the aforementioned, a flexible circuit sheet is connected to the actuator unit, but the electric devices in which a flexible circuit sheet is used are not limited to actuator units. A flexible circuit sheet may be used in a variety of electrical device having a plurality of electric terminals.
In order to mass produce flexible circuit sheets, a continuous tape is used which has a plurality of flexible circuit sheets thereon. When the continuous tape is used, the production efficiency of the flexible circuit sheets will improve.
When the continuous tape is used to mass-produce flexible circuit sheets, a method is used in which solder material is adhered to lands formed on the continuous tape, and then the continuous tape is cut and separated into a plurality of flexible circuit sheets. According to this method, the work efficiency of adhering solder material to the lands formed on the flexible circuit sheet will improve.
The electrical terminals formed on an electric device such as an actuator unit may be grouped into a first row of electric terminals and a second row of electric terminals. The first row of electric terminals extends along a first straight line. The second row of electric terminals extends along a second straight line that is parallel with the first straight line. The direction, in which the first straight line and the second straight line extend, is the first direction in the present specification. The direction that is perpendicular to the first direction is a second direction. The first straight line and the second straight line are separated in the second direction.
The flexible circuit sheet that will be connected to this type of electric device must have a first row of lands that are aligned along the first direction, and a second row of lands that are aligned parallel thereto. The first row of lands and the second row of lands must be separated in the second direction.
When the continuous tape is used to mass-produce the flexible circuit sheets, each flexible circuit sheet including a first row of lands and a second row of lands, the direction in which the continuous tape extends is the second direction, and the width direction of the continuous tape is the first direction. In other words, the first row of lands and the second row of lands will be formed so as to extend in the width direction of the continuous tape. The first row of lands and the second row of lands are separated in the direction in which the continuous tape extends. When this done, a plurality of flexible circuit sheets can be formed on one continuous tape. On one continuous tape, a plurality of flexible circuit sheets are repeated in the second direction.
When the continuous tape is used to mass produce the flexible circuit sheets, as noted above, solder material will be adhered to the lands formed on the continuous tape, and then the continuous tape will be cut. The continuous tape will pass through a solder bath in order to adhere solder material to the lands formed on the continuous tape. Solder material will be adhered to the lands while the continuous tape is passed through the solder bath. The continuous tape will pass through the solder bath by traveling in the second direction (the lengthwise direction of the continuous tape).
When the continuous tape travels in the second direction and passes through the solder bath, the quantity of solder material that will adhere to the forward side of each land in the direction of travel will not be equal to the quantity of solder material that will adhere to the rearward side of each land in the direction of travel. A portion of the solder material adhered to the forward side of each land in the direction of travel will shift to the rearward side of each land in the direction of travel. Because of this, the quantity of solder material that adheres to the forward side of each land in the direction of travel will often be insufficient, and the quantity of solder material that adheres to the rearward side of each land in the direction of travel will often be excessive. To be precise, the quantity of solder per unit of surface area that adheres on the forward side of a land in the direction of travel will often be insufficient, and the quantity of solder per unit of surface area that adheres on the rearward side of a land in the direction of travel will often be excessive.
As noted above, after solder material has been adhered to the first row of lands and the second row of lands, the continuous tape will be cut and separated into a plurality of flexible circuit sheets. By cutting off the end portions of the lands on which solder material has been adhered, a first row of lands and a second row of lands will be formed on both sides of the flexible circuit sheet.
With the first row of lands, if it is assumed that the end portions that will be cut off are on the rearward side in the direction of travel, and the lands that will be effectively used are on the forward side in the direction of travel, then with the second row of lands, the end portions that will be cut off are on the forward side in the direction of travel, and the lands that will be effectively used are on the rearward side in the direction of travel. In this ease, with the first row of lands, the quantity of solder per unit of surface area of the lands will often be insufficient. On the other hand, with the second row of lands, the quantity of solder per unit of surface area of the lands will often be excessive.
When the quantity of solder is insufficient on the first row of lands and the quantity of solder is excessive on the second row of lands, the solder joint between the first row of lands and the first row of electric terminals will not be homogeneous with the solder joint between the second row of lands and the second row of electric terminals, and thus the solder joints will often be poor.
Test electric terminals are often formed on a flexible circuit sheet. In this case, each test electric terminal is formed in a position that is continuous with one corresponding land. The test electric terminals are employed in order to test whether electric signals will be correctly transmitted to each land on the flexible circuit sheet.
When test electric terminals are formed on a flexible circuit sheet, there will be, along the direction of travel of the continuous tape, a group of lands in which lands are positioned on the forward side in the direction of travel and test electric terminals are positioned on the rearward side in the direction of travel, and a group of lands in which the test electric terminals are positioned on the forward side in the direction of travel and the lands are positioned on the rearward side in the direction of travel. With the former group of lands, the quantity of solder adhered to each land will be insufficient, because solder flows from the lands on the forward side in the direction of travel to the test electric terminals on the rearward side in the direction of travel. With the latter group of lands, the quantity of solder adhered to each land will be excessive, because after solder flows from the electric terminals on the forward side in the direction of travel to the lands on the rearward side in the direction of travel. When the test electric terminals are formed, the difference in the quantity of solder adhered to the lands on the forward side of the direction of travel and the quantity of solder adhered to the lands on the rearward side in the direction of travel will be even greater.
The electrical terminals formed on an electric device such as an actuator unit may be grouped into a first row of electric terminals and a second row of electric terminals. The first row of electric terminals extends along a first straight line. The second row of electric terminals extends along a second straight line that is parallel with the first straight line. The direction, in which the first straight line and the second straight line extend, is the first direction in the present specification. The direction that is perpendicular to the first direction is a second direction. The first straight line and the second straight line are separated in the second direction.